The superfamily of serotonin receptors (5-HT) includes 7 classes (5-HT1-5-HT7) encompassing 14 human subclasses [D. Hoyer, et al., Neuropharmacology, 1997, 36, 419]. The 5-HT6 receptor is the latest serotonin receptor identified by molecular cloning both in rats [F. J. Monsma, et al., Mol. Pharmacol., 1993, 43, 320; M. Ruat, et al., Biochem. Biophys. Res. Commun., 1993, 193, 268] and in humans [R. Kohen, et al., J. Neurochem., 1996, 66, 47]. Compounds with 5-HT6 receptor affinity are useful for the treatment of various disorders of the Central Nervous System and of the gastrointestinal tract, such as irritable intestine syndrome. Compounds with 5-HT6 receptor affinity are also useful in the treatment of anxiety, depression and cognitive memory disorders [M. Yoshioka, et al., Ann. NY Acad. Sci., 1998, 861, 244; A. Bourson, et al., Br. J. Pharmacol., 1998, 125, 1562; D. C. Rogers, et al., Br. J. Pharmacol. Suppl., 1999, 127, 22P; A. Bourson, et al., J. Pharmacol. Exp. Ther., 1995, 274, 173; A. J. Sleight, et al., Behav. Brain Res., 1996, 73, 245; T. A. Branchek, et al., Annu. Rev. Pharmacol. Toxicol., 2000, 40, 319; C. Routledge, et al., Br. J. Pharmacol., 2000, 130, 1606]. It has been shown that typical and atypical antipsychotic drugs for treating schizophrenia have a high affinity for 5-HT6 receptors [B. L. Roth, et al., J. Pharmacol. Exp. Ther., 1994, 268, 1403; C. E. Glatt, et al., Mol. Med., 1995, 1, 398; F. J. Mosma, et al., Mol. Pharmacol., 1993, 43, 320; T. Shinkai, et al., Am. J. Med. Genet., 1999, 88, 120]. Compounds with 5-HT6 receptor affinity are useful for treating infant hyperkinesia (ADHD, attention deficit/hyperactivity disorder) [W. D. Hirst, et al., Br. J. Pharmacol., 2000, 130, 1597; C. Gérard, et al., Brain Research, 1997, 746, 207; M. R. Pranzatelli, Drugs of Today, 1997, 33, 379]. Moreover, it has been shown that the 5-HT6 receptor also plays a role in food ingestion [Neuropharmacology, 2001, 41, 210-219]. Food ingestion disorders, particularly obesity, are a serious, fast growing threat to the health of humans of all age groups, since they increase the risk of developing other serious, even life-threatening diseases such as diabetes or coronary diseases.
Tetrahydro-β-carbolines has shown affinity for other serotonin receptors such as 5-HT2A, 5-HT2B and 5-HT2C [patent WO 97/00871; J. E. Audia, et al., J. Med. Chem., 1996, 39, 2773-2780].
Patents WO 02/064590, WO 02/064591, WO 02/088123 and WO 02/098875 disclose tetrahydro-β-carbolines as inhibitors of cyclic guanosine 3′,5′-monophosphate specific phosphodiesterase (cGMP-specific PDE), in particular PDE5 and their utility in the treatment of cardiovascular disorders and erectile dysfunction.
Patent WO 99/33800 discloses tetrahydro-β-carbolines as inhibitors of factor Xa and their utility in thromboembolic diseases.
Surprisingly, it has been found that the substituted tetrahydro-β-carbolines compounds of general formula (I) given below show good to excellent affinity for 5-HT6 receptors. These compounds are therefore particularly suitable as pharmacologically active agents in a medicament for the prophylaxis and/or treatment of disorders or diseases related to 5-HT6 receptors.